Primary exercises
- Manually created factor.
In a study participants were asked whether their sport activity is none, oncePerWeek, severalPerWeek or daily.
Build a proper factor for the responses below and store it in a variable w.
Print the factor.
Write the code to count the numbers of occurrences of each level and print the counts.
severalPerWeek, none, none, oncePerWeek, oncePerWeek, oncePerWeek, oncePerWeek, ?, none, none
v <- c( "severalPerWeek", "none", "none", "oncePerWeek", "oncePerWeek", "oncePerWeek", "oncePerWeek", NA, "none", "none" )
w <- factor( v, levels = c( "none", "oncePerWeek", "severalPerWeek", "daily" ) )
w
[1] severalPerWeek none none oncePerWeek oncePerWeek oncePerWeek oncePerWeek
[8] <NA> none none
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 5 x 2
f n
<fct> <int>
1 none 4
2 oncePerWeek 4
3 severalPerWeek 1
4 daily 0
5 <NA> 1
- A factor with a random content.
Read help about the function sample.
Then study and try the following lines of code to understand the results.
Next, understand why an error is generated and use replace argument to generate a vector with 100 samples.
Store this vector in a variable v and build a factor w from it.
Finally, count the numbers of occurrences of each level in w.
Ensure, that levels are in order provided in the variable lvl.
lvs <- c( "none", "oncePerWeek", "severalPerWeek", "daily" )
sample( lvs, 3 )
[1] "severalPerWeek" "daily" "oncePerWeek"
sample( lvs, 3 )
[1] "daily" "none" "oncePerWeek"
sample( lvs, 3 )
[1] "severalPerWeek" "none" "daily"
sample( lvs, 100 )
Error in sample.int(length(x), size, replace, prob): cannot take a sample larger than the population when 'replace = FALSE'
v <- sample( lvs, 100, replace = TRUE )
w <- factor( v, levels = lvs )
w
[1] oncePerWeek daily daily daily severalPerWeek oncePerWeek oncePerWeek
[8] severalPerWeek severalPerWeek severalPerWeek none oncePerWeek daily none
[15] oncePerWeek oncePerWeek none severalPerWeek severalPerWeek daily oncePerWeek
[22] none none oncePerWeek none daily none severalPerWeek
[29] none none daily daily oncePerWeek oncePerWeek oncePerWeek
[36] oncePerWeek daily daily severalPerWeek daily severalPerWeek oncePerWeek
[43] none daily oncePerWeek daily oncePerWeek none severalPerWeek
[50] daily severalPerWeek oncePerWeek oncePerWeek none none daily
[57] daily oncePerWeek oncePerWeek none severalPerWeek none severalPerWeek
[64] severalPerWeek oncePerWeek none daily none none daily
[71] severalPerWeek severalPerWeek oncePerWeek daily daily severalPerWeek none
[78] oncePerWeek none daily oncePerWeek severalPerWeek severalPerWeek daily
[85] oncePerWeek oncePerWeek daily daily oncePerWeek daily oncePerWeek
[92] severalPerWeek daily daily none none daily oncePerWeek
[99] none severalPerWeek
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 4 x 2
f n
<fct> <int>
1 none 23
2 oncePerWeek 28
3 severalPerWeek 21
4 daily 28
- Reordering factor levels.
When a factor is shown on an axis of a plot, the order is given by its levels.
The factor w from the previous exercise will be then shown in this order: none, oncePerWeek, severalPerWeek, daily.
But for a picture in a manuscript the following order might be needed: daily, severalPerWeek, oncePerWeek, none.
Apply to w one of the fct_ functions from the tidyverse library to produce a factor w2 with the requested order.
Show the levels of w2.
Again show the number of elements of each level in w2 and compare it with the table of the previous exercise.
w2 <- fct_relevel( w, c( "daily", "severalPerWeek", "oncePerWeek", "none" ) )
levels( w2 )
[1] "daily" "severalPerWeek" "oncePerWeek" "none"
fct_count( w2 )
# A tibble: 4 x 2
f n
<fct> <int>
1 daily 28
2 severalPerWeek 21
3 oncePerWeek 28
4 none 23